The isolation of yeasts from grapes was performed as described
previously (Dimakopoulou et al., 2008) with small modifications.
Grape berries belonging to cv. ‘‘Cabernet sauvignon’’ and
‘‘Maratheftiko’’ – a grape variety indigenous to Cyprus (Hvarleva
et al., 2005) – were sampled from six vineyards in Koilani, Agios
Amvrosios, Pachna and Arsos, representative of the major grapegrowing
areas of Limassol district, an important wine-producing
area in Cyprus. Grape sampling was carried out in 2010 and epiphytic
yeasts were recovered from the surface of grape berries.
Ten plants were marked along two major diagonals of each vineyard.
Three bunches were collected from the central part of each
plant. The samples were kept in paper bags and stored in portable
refrigerators during transfer to the laboratory for isolation of
yeasts. From each vineyard ten different bunches were randomly
selected and from each bunch ten berries were collected and transferred
in sterile distilled water (SDW) containing 0.02% Tween-20.
The berries were shaken at room temperature for 10 min at
150 rpm and then 10-fold dilutions were prepared in SDW. From
each dilution 200 ll were plated in Petri dishes containing yeast
malt agar (YMA, containing 3 g yeast extract, 3 g malt extract, 5 g
bactopeptone, 10 g glucose, 15 g agar per lt). Petri dishes were of A. tubingensis or SDW containing 0.01% Agral as negative control.
The A. tubingensis isolate was grown for 7 days on potato dextrose
agar (PDA) at 25 C and the conidial suspension was obtained
by washing plates with SDW containing 0.02% Tween-20 (Sigma–
Aldrich). The berries were incubated at 25 C for 7 days in plastic
boxes under 100% relative humidity that was maintained by the
addition of 30 ml sterile water to each box. Each yeast isolate test
consisted of fifteen berries and the experiments were repeated at
least twice. The percentage of fungal growth inhibition was determined
7 days after A. tubingensis inoculation, using the formula:
100 [(diameter of fungal colony growth on berry treated with
yeast/without yeast) 100].